pub fn prepare_admm_spectral(
local_field: &[f64],
grid: &Grid,
bdir: (f64, f64, f64),
rho: f64,
) -> (Fft3dWorkspace, Vec<f64>, Vec<Complex64>)Expand description
Pre-compute ADMM spectral operators (dipole kernel, inverse operator, and RHS).
Shared by TV-ADMM and NLTV. Returns (fft_workspace, inv_a, f_hat).